The present invention concerns a device for regulating the flow of fluid or gas supplied to, and for regulating pressure within, a cavity. In particular, the present invention concerns an insufflation device for introducing a gas into an intra-abdominal cavity.
Known insufflation devices introduce limited quantities of an insufflation gas, such as carbon dioxide (CO.sub.2) for example, into a human body to enlarge a body cavity during certain surgical procedures. However, the amount of CO.sub.2 introduced into the body within a certain period of time must be limited because CO.sub.2 is absorbed by the blood and increases the carbonic acid present in veineous blood. Some carbonic acid naturally occurs in veineous blood due to work performed by muscles. However, under normal conditions, if too much CO.sub.2 per unit time is artificially introduced, the dissolving power of the blood may be exceeded (i.e., gas emboly) leading to the potential for gas bubbles being formed in the coronary vein which endangers the life of the patient.
U.S. Pat. No. 4,207,887 ("the '887 patent") describes a gas insufflation apparatus in which a pressure gauge, which is connected to the body cavity by a measuring duct, closes a solenoid valve when a critical pressure is reached in the body cavity. The valve can be reopened when the intra-cavity pressure falls below a predetermined pressure. Unfortunately, the solenoid valve used in the '887 patent cannot be opened and closed at high frequencies and therefore cannot be used to precisely control the intra-cavity pressure or to control the flow rate of gas to the cavity. Moreover, the intra-abdominal cavity pressure cannot be predicted with an external measuring means.
U.S. Pat. No. 4,048,992 ("the '992 patent") discusses an insufflator having an arrangement for exactly measuring gas pressure and limiting gas flow. Two sensing elements arranged in an expansion cylinder are used to measure the gas pressure. A Verres needle is used to limit the rate of flow. However, the Verres needle cannot limit the pressure. Moreover, the insufflator of the '992 patent requires a series of valves. Finally, the insufflator of the '992 patent cannot predict intra-cavity abdominal pressure.
U.S. Pat. No. 3,885,590 ("the '590 patent") discusses a gas transmission and monitoring device having an adjustable control valve. The adjustable control valve is normally preset to a desired pressure and flow rate and exercises final control over gas delivered to an outlet. However, the device of the '590 patent cannot predict intra-cavity pressure.
U.S. Pat. No. 3,870,072 ("the '072 patent") discusses an insufflator including a shut-off valve which can be closed and which is connected to a drive motor. The drive motor reopens the shut-off valve after a variable regeneration time from the closing of the valve. The device of the '072 patent cannot predict the intra-abdominal cavity pressure and does not permit the pressure or flow rate to be rapidly adjusted.
U.S. Pat. No. 3,901,820 ("the '820 patent") discusses an apparatus for measuring pressure modulated gas in which a wheel or disk repeatedly expands and contracts a bellow via a coupling link. However, the apparatus of the '820 patent is related to infrared analyzers and is not used as an insufflation device or valve.
In view of the above described limitations of the prior art gas valves and insufflation devices, the goal of the present invention is to provide a valve which has a nearly infinitely adjustable displacement volume and which permits an intra-abdominal cavity pressure to be predicted, in real time, without requiring an intra-abdominal measurement.